Teen-agers are much concerned for their appearances. Their clothes reflect their living conditions and serve as a means to represents themselves as well. They also show great concern for the clothes of students of an age. So to guide their clothing behaviours in school plays a very important role in the living guidance of students. From this point, this study was aimed at examing closely the differences of recations as to the girl students' clothing behaviours between boy students and girl students of high school, and the correlation between environment condition and reaction upon the clothing behaviours of girl students. To check the physical environment condition of the family, the family circumstances test, made and standardized by Jung Won Sik, was used. To check the clothing behaviours of girl students, four items-modesty, fashion and esthetics were made and each item had five questions, wihich comprised fifteen questons all told. The subjects of this study included students in eight high schools located in Incheon, totaling 930 boys and girls. The results of this study were summarized as follows: 1. There are great differences in students' reaction upon girl students' clothing behaviours according to their physical circumstances level, sex, grade years and the degree of concern for other sex. (A) The correlation between students' physical circumstances level and their reaction upon the girl students' clothing behaviours is high in all the three items. The higher the students' circumstancses level is, the lower their reaction upon modesty is, and the higher their reaction upon fashion. In case of esthetics, only girl students show great concern for it. (B) As to the reaction upon the girls students' clothing behaviours by sex, girls show higher concern for modesty, fashion and esthetics than boys. (C) As to the reaction upon the girl students' clothing behaviours by the grade years, the first year students as a whole show higher concern for modesty than second grade year students. (D) As to the reaction upon the girl students' clothing behaviours by the degree of concern for other six, the more concern both the boy and the girl students have for other sex, the higher their reactions are upon fashion and esthetics, but the lower upon modesty. 2. From the point of reactions upon the girl students' clothing behaviours, (A) as to fashion, free variables can explain by 7.8 percent the degree of concern for other sex, physicial circumstances level, and sex in that order. (B) as to fashion, free variables can explain by 5.4 persent the concern for other sex, physicial circumstances level, and sex in that order. (C) as to esthetics, free variables can explain by 4.8 percent the concern for other sex, physicial circumstances level, and sex in that order. From the above analysis, the following are included: The concern for other sex has the greatest influence on the girl students clothing behaviours, the physicial circumstances level the nest, sex the third and the grade year the last.